The offences were committed using sophisticated electronic methods to add false credits to the machines, which were then paid out at amounts of up to £500 a time. The gang were often committing several offences a day.

The police investigation also uncovered the activities of the seventh member of the gang, Darren Carrick, also from Portsmouth, whose bank accounts were used to move tens of thousands of pounds, usually in £1 coins.

Carrick was convicted under Money Laundering legislation and sentenced to 18 months imprisonment. He also faces the possible forfeiture of some £75,000 recovered by police.

Det Insp Kevin McGuire of Thames Valley Police, said:

“The gaming industry was suffering high losses due to the activities of organised criminal gangs such as these. Individual offences were reported and arrests often made but sentences were usually minimal as they were for single offences.

“Operation Sweepstake was launched by Thames Valley Police’s Major Crime team with a view to working together with the gaming industry to properly reflect the level of offending this gang were responsible for and to bring them together in front of a court for a criminal conspiracy.

"A large number of offences were identified from which we selected 50 to prosecute. The sentences handed out today reflect the seriousness of their crimes.”